Browsing Faculty of Science by Title
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Shaikh, M.; Moleele, N.; Ekosse, G.I.E.; Totolo, O.; Atlhopheng, J. (JASEM http://www.ajol.info/index.php/jasem/article/view/43693/27216, June NaN, 2006)[more][less]
Abstract: Since 1988 Botswana has been experiencing an unprecedented increase in vehicular traffic which is suspected to be having contamination effects on soils along heavily used roads in the country. This study aimed at understanding the contamination trends of heavy metals on soils due to vehicular emissions. The soil physicochemistry (bulk density, particle size distribution, pH, electrical conductivity and cation exchange capacity), mineralogy (using x-ray diffraction techniques) and heavy metals (Cd, Pb, Cu and Zn) concentrations were determined for soil samples obtained along the roadside at 2m, 4m, 6m and 100 m of the Gaborone – Tlokweng Emigration/Immigration Boarder Post Road, which is one of the busiest in the country. Bulk density of soil samples were from 1.19 to 1.4; and sand, loamy sand and sandy loam textural classes constituted the soil samples. The soil pH was from 5.09 to 8.57; the EC ranged from 6.27 μS cm-1to 20.3 27 μS cm-1 and the CEC values were from 10.2 meq100g-1 to 27.2 meq100g-1. Clay minerals were identified in the samples as well as feldspar and quartz. The concentration levels for Pb were from 0 mgkg-1 to 71 mgkg-1; Zn were from 5.23 mgkg-1 to 51.26 mgkg-1 ; Cu were from 0.3 mgkg-1 to 18.1 mgkg-1 and Cd 0 mgkg-1 to 2.4 mgkg-1 . The interplay of soil physico-chemistry and mineralogy on heavy metals concentrations is discussed. Although levels of heavy metals concentrations fell below normal ranges, the values obtained were generally higher than those from some developed and developing countries. URI: http://hdl.handle.net/10311/361 Files in this item: 1
Shaikh_JASEM_2006.pdf (1.018Mb) -
Bonyongo, M.C.; Mubyana, T. (South African Journal of Science, http://www.sajs.co.za/, NaN, 2004)[more][less]
Abstract: WETLANDS SUCH AS THE OKAVANGO Delta, located in semi-arid regions, are of great ecological, environmental and socio-economic importance. In most cases, however, few data exist on nutrient cycling in these areas. This paper presents preliminary results of an ongoing study, which investigates the influence of seasonal flooding on soil nutrient status in the different vegetation communities of the delta. Soil K, Na, and pH significantly increased with a decrease in soil moisture, with the values increasing from the primary floodplains to the islands communities. Available P, Ca and Mg decreased as the elevation gradient increased from the riverbed. Although nutrient status generally was highest in the floodplain vegetation areas adjacent to the riverbed, there was no significant difference in available P, Ca and Mg within the vegetation communities. Calcium levels in the different vegetation zones were more influenced by rainfall than floodplain vegetation community. Higher soil Ca was observed in the rainy season, while elevated Mg was recorded after the rains. Overall, these results indicate that flooding is an essential aspect of the Okavango Delta as it may be a primary source of some of the soil nutrients that support the high diversity of plants sustaining the delta’s ecosystem. URI: http://hdl.handle.net/10311/401 Files in this item: 1
Soil nutrient status.pdf (1.635Mb) -
Mosweu, S. (Academic Journals, http://www.academicjournals.org/SRE, NaN, 2008)[more][less]
Abstract: The distribution of selected soil properties, selected woody vegetation properties, and land use in a lunette dune-pan system were investigated in the Sekoma area, which is located within the IGBP Kalahari Transect (KT) in Botswana. KT was established by the IGBP for studies focusing on both regional and global environmental changes. The study showed that the lunette dune-pan system exhibited substantial spatial heterogeneity in the distribution of the selected soil attributes. This limited the extent to which variation in the investigated vegetation characteristics could be explained on the basis of soil resources distribution. Encroacher plant species were found to be prevalent in the sites that were subjected to higher land use pressure. The study concluded that land use, particularly browsing, was the principal environmental driver and had precedence over the distribution of the selected soil attributes in relation to woody plant properties in the lunette dune-pan system. URI: http://hdl.handle.net/10311/964 Files in this item: 1
Mosweu_SRE_2008.pdf (783.3Kb) -
Wright, C.; Kgaswane, E.M.; Kwadiba, M.T.O.; Simon, R.E.; Nguuri, T.K.; McRae-Samuel, R. (Elsevier Science Ltd. www.elsevier.com/locate/lithos, NaN, 2003)[more][less]
Abstract: Events induced by deep gold-mining activity on the edge of the Witwatersrand basin dominate the seismicity of South Africa. The deployment of 54 broad-band seismic stations at 84 separate locations across southern Africa between April 1997 and April 1999 (Kaapvaal network) enabled the seismicity of South Africa to be better defined over a 2-year period. Seismic events located by the South African national network, and by localized seismic networks deployed in mines or across goldmining areas, were used to evaluate earthquake location procedures and to show that the Kaapvaal network locates mininginduced tremors with an average error of 1.56 ± 0.10 km compared with 9.50 ± 0.36 km for the South African network. Travel times of seismic events from the mines recorded at the Kaapvaal network indicate regional variations in the thickness of the crust but no clearly resolved variations in seismic wavespeeds in the uppermost mantle. Greater average crustal thicknesses (48–50 km compared with 41–43 km) are observed in the northern parts of the Kaapvaal craton that were affected by the Bushveld magmatism at 2.05 Ga. Estimates of average crustal thickness for the southern part of the Kaapvaal craton from receiver functions (38 km) agree well with those from refracted arrivals from mining-induced earthquakes if the crustal thicknesses below the sources are assumed to be 40–43 km. In contrast, the average crustal thickness inferred from refracted arrivals for the northern part of the Kaapvaal craton is larger by about 7 km (51 km) than that inferred from receiver functions (44 km), suggesting a thick mafic lower crust of variable seismic properties due to variations in composition and metamorphic grade. Pn wavespeeds are high (8.3–8.4 km/s), indicating the presence of highly depleted magnesium-rich peridotite throughout the uppermost mantle of the craton. Seismic Pg and Sg phases indicate that the upper crust around the Witwatersrand basin is comparatively uniform in composition when averaged over several kilometres. URI: http://hdl.handle.net/10311/280 Files in this item: 1
Wright_L71_2003.pdf (3.483Mb) -
Masesane, I.; Steel, P. (Elsevier Ltd; www.elsevier.com/locate/tetlet, June 21, 2004)[more][less]
Abstract: The Diels-Alder adduct of ethyl (E)-3-nitroacrylate and furan provides a versatile template for the stereoselective synthesis of mono and dihydroxylated derivatives of 2-aminocyclohexanecarboxylic acid (ACHC). The hydroxylated ACHC derivatives can be considered to be useful building blocks for B-peptides. URI: http://hdl.handle.net/10311/235 Files in this item: 2
license.txt (1.998Kb)Stereoselective routes to 3-hydroxy.pdf (721.3Kb) -
Chola, J.; Masesane, I.B. (Elsevier Ltd. www.elsevier.com/ locate/tetlet, NaN, 2008)[more][less]
Abstract: Stereoselective syntheses of racemic (1S,2R,3R,4R,5S,6R)- and (1S,2R,3R,4S,5S,6R)-3,4,5,6-tetrahydroxy derivatives of 2-aminocyclohexanecarboxylic acid have been achieved by a stereospecific Diels–Alder reaction between furan and maleic anhydride, a Curtius rearrangement and hydroxylation reactions. URI: http://hdl.handle.net/10311/325 Files in this item: 1
Stereoselective sythesis of 3.pdf (1.100Mb) -
Ogwu, F.J.; Talib, M.; Aderounmu, G.A. (Science Publications, http://www.scipub.org/scipub/c4p.php?j_id=JCS, NaN, 2007)[more][less]
Abstract: Recent works on Available Bit Rate (ABR) traffic control have generated efficient control schemes for ABR traffic on Asynchronous Transfer Mode (ATM) network. This study examines the improved performance envisaged if these control schemes adjust dynamically to the varying ABR bandwidth capacity in a stochastic manner instead of conventional deterministic approach. The performance difference between setting explicit rate deterministically for transmitting ABR sources and doing the same stochastically using a learning automaton is of particular interest. The learning automaton used is the Stochastic Estimator Learning Automaton (SELA). The performance difference is measured by comparing the congestion levels of the SELA-based control scheme with the reference deterministic control mechanism. Simulation results show that the stochastic estimator gives a better performance. The higher average congestion level experienced by the conventional deterministic approach is mainly due to the propagation time delay in the closed-loop feedback control schemes. URI: http://hdl.handle.net/10311/817 Files in this item: 1
Ogwu_JCS_2007.pdf (502.1Kb) -
Jain, P.K.; Lungu, E.M. (Elsevier Science Ltd: http://www.elsevier.com/wps/find/journaldescription.cws_home/969/description#description, NaN, 2002)[more][less]
Abstract: Abstract Harmonic analysis of sunshine duration and solar irradiation measured at Sebele, Botswana is carried out. The data used consists of the monthly averages and the Julian-days averages of sunshine duration and solar irradiation sequences. This study involves splitting the time series into deterministic and stochastic components, and determining the proportion of the variance explained by each component. The stochastic component is analyzed for persistence using the Box and Jenkins technique. It is found that the stochastic component for monthly averages solar radiation series is best described by the second-order autoregressive Markov process, while that for Julian-days averages series has no memory. URI: http://hdl.handle.net/10311/138 Files in this item: 2
license.txt (1.998Kb) -
Gatsinzi, J-B.; Kwashira, R. (Nova Science Publishers, Inc.; www.novapublishers.com; reprinted with permission from Nova Science Publishers, Inc., NaN, 2007)[more][less]
Abstract: Let X be a finite product of even dimensional spheres, we show that the string homology of X contains a finite product of copies of the Witt Lie algebra. URI: http://hdl.handle.net/10311/162 Files in this item: 1
gatsinzi-kwashira1.pdf (139.6Kb) -
Prakash, J.; Ogulu, A. (Elsevier; www.elsevier.com/locate/ichmt, July NaN, 2007)[more][less]
Abstract: A mathematical model for the pulsatile blood flow in a small vessel in a cardiovascular system with a mild stenosis is analyzed. Blood is modeled as a power low fluid and the differential approximation for the heat flux is invoked in the energy equation. The effect of heat transfer on the velocity is computed and discussed. URI: http://hdl.handle.net/10311/226 Files in this item: 2
license.txt (1.998Kb)Prakash_ICHMT_2007.pdf (772.9Kb) -
Obuseng, V.; Nareetsile, F.; Kwaambwa, H.M. (Elsevier Science Ltd, www.elsevier.com/locate/aca, NaN, 2012)[more][less]
Abstract: Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II)>Cu(II)>Cd(II)>Ni(II)>Mn(II) and Zn(II)>Cu(II)>Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn>Cd >Cu> Ni>Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8. URI: http://hdl.handle.net/10311/1039 Files in this item: 1
Obuseng_ACA_2012.pdf (886.0Kb) -
Lerouge, C.; Cailteux, J.; Kampunzu, A.B.; Milesi, J.P.; Fle´hoc, C. (Elsevier www.elsevier.com/locate/jafrearsci, NaN, 2005)[more][less]
Abstract: Luiswishi is a Congo-type Neoproterozoic sediment-hosted stratiform Cu–Co ore deposit of the Central Africa Copperbelt, located northwest of Lubumbashi (DRC). The ores form two main Cu–Co orebodies hosted by the Mines Subgroup, one in the lower part of the Kamoto Formation and the other at the base of the Dolomitic Shales Formation. Sulphides occur essentially as early parallel layers of chalcopyrite and carrolite, and secondarily as late stockwork sulphides cross-cutting the bedding and the early sulphide generation. Both types of stratiform and stockwork chalcopyrite and carrolite were systematically analyzed for sulphur isotopes, along the lithostratigraphic succession of the Mine Series. The quite similar d34S values of stratiform sulphides and late stockwork sulphides suggest an in situ recrystallization or a slight remobilization of stockwork sulphides without attainment of isotopic equilibrium between different sulphide phases (chalcopyrite and carrolite). The distribution of d34S values ( 14.4& to +17.5&) combined with the lithology indicates a strong stratigraphic control of the sulphur isotope signature, supporting bacterial sulphate reduction during early diagenesis of the host sediments, in a shallow marine to lacustrine environment. Petrological features combined with sulphur isotopic data of sulphides at Luiswishi and previous results on nodules of anhydrite in the Mine Series indicate a dominant seawater/lacustrine origin for sulphates, precluding a possible hydrothermal participation. The high positive d34S values of sulphides in the lower orebody at Luiswishi, hosted in massive chloritic–dolomitic siltite (known as Grey R.A.T.), fine-grained stratified dolostone (D.Strat.) and silicified-stromatolitic dolomites alternating with chloritic–dolomitic silty beds (R.S.F.), suggest that they were probably deposited during a period of regression in a basin cut off from seawater. The variations of d34S values (i.e. the decrease of d34S values from the Kamoto Formation to the overlying Dolomitic Shales and then the slight increase from S.D.2d to S.D.3a and S.D.3b members) are in perfect agreement with the inferred lithological and transgressive–regressive evolution of the ore-hosting sedimentary rocks [Cailteux, J., 1994. Lithostratigraphy of the Neoproterozoic Shaba-type (Zaire) Roan Supergroup and metallogenesis of associated stratiform mineralization. In: Kampunzu A.B., Lubala, R.T. (Eds.), Neoproterozoic Belts of Zambia, Zaire and Namibia. Journal of African Earth Sciences 19, 279–301]. URI: http://hdl.handle.net/10311/390 Files in this item: 1
Kampunzu2005SulpherIsotope.pdf (1.156Mb) -
Koosimile, A.T. (Elsevier, www.elsevier.com/locate/ijedudev, NaN, 2005)[more][less]
Abstract: This paper focuses on teachers’ experiences with implementing a modified International General Certificate of Secondary Education (IGCSE) physics syllabus in Botswana. The syllabus, characterised by a new organisational and pedagogic paradigm, is a significant shift from the traditional ‘‘teacher-proof’’ syllabus to one that is flexible, nonprescriptive and student-centred. Through data from discussions and interviews with teachers, it emerged that policy statements on the nature of the syllabus were contradictory and confusing to guide both the adoption and implementation of the syllabus. It also emerged that teachers accorded the core curriculum component of the syllabus a lower priority and status than the extended curriculum component. The findings also reveal that considerable overlaps in the core and extended curriculum components of the syllabus blurred the distinction between the two as well as weakening prospect of fidelity of adoption and implementation. The resulting ‘innovation gap’ invariably means that the ideals of the syllabus and the associated paradigm shifts are possibly not realised in teaching in Botswana. The findings generally underscore the importance of clear guidance and policy statements on any new syllabus, and indeed, a new curriculum. Possible directions in future research would be to investigate innovation gaps that might be manifest in teaching. URI: http://hdl.handle.net/10311/499 Files in this item: 1
Koosimile2005ICGSEphysics.pdf (1.142Mb) -
Masale, M. (Elsevier Science Ltd. www.elsevier.com/locate/physb, February NaN, 2002)[more][less]
Abstract: The experimental techniques of attenuated total reflection and grating-coupling were originally employed separately as probes for surface polaritons. However, as far back as the mid-1970s, some value was found in actually combining them into a single tool for probing elementary surface excitations. In this article, the theory of the two methods combined into one probe for surface polaritons is presented. The main results of the calculations, here, are the firstorder diffuse reflectivities, which arise due to the presence of a classical grating. For the ease of presentation, only a semi-infinite specimen is considered and the grating is thought to be deposited only on one interface. The discussion highlights the advantages the combined technique has over either of the two methods when each is employed on its own. URI: http://hdl.handle.net/10311/195 Files in this item: 2
license.txt (1.998Kb) -
Masale, M. (Elsevier Science Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/505712/description#description, NaN, 2003)[more][less]
Abstract: The experimental techniques of attenuated total reflection (ATR) and grating coupling were originally employed separately as probes for polaritons. The combined technique of these methods into a single probe is a very versatile tool for probing elementary surface excitations. A theoretical investigation of this single probe for surface polaritons, ATRgrating coupling, is undertaken. The emphasis is on the calculations of first-order diffuse reflectivities, which arise due to the presence of a classical grating. More specifically, the ATR set-up in the Otto configuration is considered and for ease of presentation of the results, a classical grating is thought to be deposited on only one interface of a surface-active thin-film specimen. The discussion highlights the advantages the combined technique has over either of the two methods when each is employed on its own. URI: http://hdl.handle.net/10311/233 Files in this item: 2
license.txt (1.998Kb) -
Kumar, P.; Thangaraj, R.; Sathiaraj, T.S. (Springer Netherlands, NaN, 2008)[more][less]
Abstract: The melt-quenched Sn10Sb20Se70 sample in the bulk form was used to prepare films on well-cleaned glass substrates by thermal evaporation method. The activation energy for glass transition (apparent) and crystallization has been analyzed by using the Kissinger formulation. The X-ray diffraction study shows the crystallization of Sb2Se3 phase in the major proportion as compared to the SnSe2 phase. The SEM images film of the show the appearance of spherical globules upon annealing below the glass transition temperature. The effect of annealing temperature on the electrical and optical properties has been studied. A linear fit between DE and Eo is observed, indicating the validity of Meyer–Neldel rule with the change in the annealing temperature. Description: some mathematical symbols may not come as they are in the title and abstract. URI: http://hdl.handle.net/10311/691 Files in this item: 1
Thermal analysis.pdf (949.2Kb) -
Thermal annealing dependence of some physical propertiesof Bi-substituted Sn–Sb–Se glassy thin filmsAhmad, M.; Thangaraj, R.; Sathiaraj, T.S. (EDP Sciences, NaN, 2009)[more][less]
Abstract: Bulk glasses of the Sn10Sb20−xBixSe70 (0 x 8) system were prepared by the conventional melt quenching technique. Thin films were prepared by the thermal evaporation technique on glass substrates. Appearance of some crystalline phases is observed from the X-ray diffractograms after heat treatment below the glass transition temperature for 1 h. Scanning electron microscopy studies also show the presence of microcrystalline phases in the amorphous matrix after annealing for 1 h. The effect of Bi concentration and heat treatment on the optical gap and activation energy for dark conductivity were also investigated for the pristine as well as annealed films. The results are discussed on the basis of models related to the presence of defect states in chalcogenide materials. URI: http://hdl.handle.net/10311/534 Files in this item: 1
Thermal annealing dependence.pdf (822.7Kb) -
Mmopelwa, G.; Kgathi, D.L.; Molefhe, L. (Elsevier http://www.linkinghub.elsevier.com/retrieve/pii/S0261517706001440, NaN, 2007)[more][less]
Abstract: Moremi game reserve (MGR) in northern Botswana is one of southern Africa’s most popular destination because of its impressive wildlife and wilderness areas. To maintain the wilderness nature of the park and game reserve, the Government has pursued a policy of high cost-low volume which is not necessarily based on demand and supply characteristics of the tourist market. The present study determines the perceptions of self-drive tourists and clients of mobile tour operators on the prevailing park fees in MGR and uses the contingent valuation method to determine their willingness to pay (WTP) for park fees under a management scenario in which the management of the game reserve would be improved by a hypothetical international conservation organization. Data collection involved a self-fill of a questionnaire by these tourists in the game reserve. In the first scenario the mean entrance and camping suggested by nonresidents was higher than the prevailing fee. Residents suggested a lower entrance fee. In the hypothetical scenario, the mean maximum WTP for entrance and camping fee for South African and overseas tourists were higher than in the first scenario. There was a significant difference in the WTP for entrance fee between overseas tourists and South African tourists (p<0.05). Overall expenditure was significantly related to the WTP for increased park fees. The paper concludes by suggesting improvement in the MGR’s facilities for better satisfaction of tourists. URI: http://hdl.handle.net/10311/481 Files in this item: 1
Mmopelwa_TM_2007.pdf (1.545Mb) -
Gwebu, T.D. (Blackwell Publishing Ltd, http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1467-9663, NaN, 2006)[more][less]
Abstract: This paper investigates the extent to which the differential urbanisation model is applicable to Botswana by using empirical data obtained from periodic censuses, supportive documentary information and observations from personal on-going research on urbanisation and migration. Differential urbanisation refers to the cyclic spatio-temporal growth trends that the elements of human settlement hierarchies undergo, in response to migration. Empirical studies have verified the validity of differential urbanisation in the United States, Europe, India and South Africa. These areas, unlike Botswana, have longer histories of urbanisation, larger population sizes, denser population distributions, and higher levels of economic development. Current research interest is focused on investigating the theoretical applicability of the differential urbanisation model to those countries at the lower end of the economic development spectrum. The rationale and thrust of this paper is to therefore investigate the relevance of differential urbanisation under unique environmental, demographic and socio-economic conditions that pertain to Botswana. Evidence from the paper shows that urbanisation in Botswana has occurred in sequenced phases that, in general, resemble those suggested by the differential urbanisation model in the following ways. First, there has been concentration in the primate city due to mainstream migration. Secondly, there has been fission leading to the fast growth of the adjacent intermediate settlements, partly as a result of deglomeration economies at the primate core accompanied by substream migration. Third, the peripheral regional and rural centres appear to be now growing relatively rapidly, in response to the implementation of decentralisation policies. URI: http://hdl.handle.net/10311/956 Files in this item: 1
Gwebu_TESG_2006.pdf (1.050Mb) -
Mapolelo, M.; Torto, N. (Elsevier; www.elsevier.com/locate/talanta, NaN, 2004)[more][less]
Abstract: [Please note that chemical formulae do not display correctly in this abstract]. Sorption properties of baker's yeast cells, characterised as Saccharomyces cerevisiae were evaluated for trace enrichment of metal ions: Cd2+, Cr3+, Cr6+, Cu2+, Pb2+ and Zn2+ from aqueous environments. Metal concentration was determined by flame atomic absorption spectrometry (FAAS). Parameters affecting metal uptake such as solution pH, incubation time, amount of yeast biomass and effect of glucose concentration (energy source) were optimised. Further studies were carried out to evaluate the effects on metal uptake after treating yeast with glucose as well as with an organic solvent. The results showed that trace enrichment of the metals under study with yeast, depends upon the amount of yeast biomass, pH and incubation time. Treatment of yeast cells with 10-20mM glucose concentration enhanced metal uptake with exception to Cr6+, whose metal enrichment capacity decreased at glucose concentration of 60 mM. Of the investigated organic solvents THF and DMSO showed the highest and lowest capacity, respectively, to enhance metal uptake by yeast cells. Trace enrichment of metal ions from stream water, dam water, treated wastewater from a sewage plant and wastewater from an electroplating plant achieved enrichment factors (EF) varying from 1 to 98, without pre-treatment of the sample. pH adjustment further enhanced the EF for all samples. The results from these studies demonstrate that yeast is a viable trace metal enrichment media that can be used freely suspended in solution to achieve very high EF in aquatic environments. URI: http://hdl.handle.net/10311/156 Files in this item: 2
license.txt (1.998Kb)mapolelotortonew.pdf (469.7Kb)